Basalt

Basalt is a fine-grained igneous rock, formed from the rapid cooling of volcanic lava. It makes up nearly all volcanic rock on earth. Around 50% silica (SiO2), its chemistry is the same as slow-cooling coarse grained gabbro – the exact ingredients will vary according to the location. It is typically dark coloured, including shades of grey, through brown and black.

It is used as stone in sculpture, architecture, construction and road building. Alternatively, it is melted and extruded into a fibre, which is converted into fabrics, felts and composites. The textiles are used as reinforcement in the production of high-strength composites, as high quality sound and thermal insulation, and fireproofing.